1. Field of the Invention
This invention relates to a method of constructing microwave systems and processing the signal by correlation.
This invention is applicable notably in tachometry, telemetry, directional servo-control and tracking, notably in robotics, the detection of heterogeneousness and discontinuity in a given material from sensors of the contact or contactless type.
2. The Prior Art
Nowadays, the main techniques utilized in contactless tachometry are based on the Doppler effect. This phenomenon is applicable in many fields and notably for ascertaining with precision the speed of a moving body by transmitting a wave of predetermined frequency towards the moving body and analysing the frequency reflected by said movable body.
It is known that when a change occurs in the distance between a source emitting a fixed frequency and a receiving aerial, the apparent frequency received by the aerial is shifted in relation to the emitter frequency. This shift is proportional to the velocity of movement of the emitter in relation to the receiver along the axis interconnecting them.
However, a tachometer based on the Doppler effect is scarcely sensitive when the distance from the source to the object under observation varies moderately with time, for example when the object is travelling in a direction perpendicular to the observation direction. In fact, the inconvenience lies in the fact that the direction of propagation of the incoming wave and of the reflected wave must lie substantially in the direction of travel of the movable body if an optimal measurement precision is desired.